1. Field of the Invention
The present invention relates to an ultrasound surgical apparatus used for treatment of living tissues by means of ultrasound vibrations and to a calibration method for the ultrasound surgical apparatus.
2. Description of the Related Art
Examples of ultrasound surgical apparatuses used for treatment of living tissues by means of ultrasound vibrations include an ultrasound-activated scalpel, ultrasound aspirator, ultrasound lithotriptor, and ultrasound trocar.
The ultrasound-activated scalpel is used to perform a coagulation process or dissection process by means of frictional heat generated when a tissue is grasped with a probe which performs ultrasound vibrations. The ultrasound-activated scalpel can operate at lower temperatures than an electrical surgical apparatus and thus causes less damage to tissues. A probe capable of high-frequency current conduction makes it easy to administer hemostatic treatment.
The ultrasound aspirator, which utilizes tissue selectivity of ultrasound, heats only fragile tissues with ultrasound vibrations and thereby emulsifies and aspirates the fragile tissues. This makes it possible to expose flexible tissues such as blood vessels without crushing.
The ultrasound lithotriptor breaks a stone or the like using an impact of ultrasound vibrations, with a probe vibrated by ultrasound being placed in direct contact with the stone or the like.
The ultrasound trocar reduces a contact overload on a living tissue using ultrasound vibrations and thereby enables puncture using a small amount of force. The ultrasound trocar, which can reduce bleeding by the coagulating effect of ultrasound vibrations, can make the field of view of an endoscope less liable to being blocked by bleeding from the abdominal wall.
Thus, ultrasound surgical apparatuses treat living tissues using ultrasound vibrations of a distal end portion of a probe joined to, i.e., mechanically coupled to, an ultrasound transducer.
With ultrasound surgical apparatuses, even if the ultrasound transducer is driven at a predetermined driving current, it was sometimes difficult to vibrate the distal end portion of the probe at a predetermined vibration strength depending on factors such as manufacturing variations, operating temperature, state of junction between the ultrasound transducer and probe, or aging of the system. Incidentally, to measure the vibration strength of ultrasound vibrations directly as amplitude, an expensive, special apparatus which uses laser Doppler effect was required, and thus it was difficult to check vibration strength at a treatment location before treatment.
International Publication No. WO 2005/094701 discloses an ultrasound irradiation method which detects state of cavitation based on a sound pressure signal to maintain a predetermined state of cavitation.
Also, Japanese Patent Application Laid-Open Publication No. 2001-87278 discloses an ultrasound aspirator which detects an actual output value (amount of amplitude) in a distal end portion of a probe based on load information about an ultrasound transducer and feeds the output value back to a controller.